In telecommunication systems signals can be distributed to destination devices over a wide area using a variety of delivery mechanisms. For example, signals may be distributed to a receiver over a wireless communication link while other signals are distributed to the receiver over a wireline link. The receiver may be able to select which of the received signals to process. The receiver can be configured to select between the signals received over the wireless link or the signals received over the wireline link.
The received signal strength at the receiver can vary over a wide range due to the differing characteristics of the wireless link or wireline link. For example, signals received over a wireless link may be attenuated due to lack of proximity, occlusions, or destructive multiple path signal combinations. Similarly, a signal received over a wireline link may be attenuated due to propagation losses through the transmission line as well as losses due to splitting of the signal. However, a wireline signal distribution system can include one or more distribution amplifiers in branches of the wireline signal distribution system in order to maintain the power within a desired range at each of the distribution system endpoints.
It is desirable for a receiver having the ability to select from a signal received over a wireless link or a signal received over a wireline link to have the ability to compensate for the wide dynamic range of input signals presented by the union of the two operating systems.
A receiver typically includes one or more variable gain amplifiers within an automatic gain control loop in order to compensate for at least a portion of the variations in the received signal strength. Continuous gain control is desirable in a receiver because it allows for closed-loop control to maintain constant signal amplitude at the output of a receiver. A receiver typically includes one or more variable gain amplifiers within an automatic gain control loop in order to compensate for at least a portion of the variations in the received signal strength. One or more continuously-variable gain elements can be distributed throughout the receiver's signal path.
However, it is difficult to design a very linear amplifier capable of amplifying large input signals in a linear fashion which simultaneously possesses continuous gain control. A further complication is the desire to implement a relatively large dynamic range over which gain control operates.